1. Field of the Invention
The present invention relates to a mount apparatus for supporting a vibration source on a base, more particularly, to an active hydraulic mount apparatus.
2. Description of the Prior Art
Conventional mounts exist for supporting and providing vibration isolation of vibration sources. One well-known application of these mounts is for supporting components of automotive vehicles. These mounts typically operate to provide engine vibration isolation while also to control the motion of the engine and connected powertrain components with respect to the vehicle frame or body structure. In many applications of engine and powertrain mounts, it is desirable to vary damping characteristics of the mount to provide selective isolation of vibrations at certain frequencies.
One such hydraulic mount apparatus is disclosed in U.S. Pat. No. 5,439,204 to Yamazo et al. The mount includes a housing that extends about and along a first axis and defines a housing chamber. A flexible body made of an elastic material is disposed in the housing chamber to define a pumping chamber within the housing chamber that is configured to be filled with a fluid. The pumping chamber is interconnected with the housing for deforming elastically in response to movement of a vibration source relative to the housing caused by an external excitation. A moving member is partially disposed in the pumping chamber for moving within the pumping chamber. An actuator is operatively coupled to the moving member for moving the moving member to create a volume change in the pumping chamber to maintain the volume of the pumping chamber to prevent a pressure increase in the pumping chamber during the deformation of the flexible body in response to the external excitation to effectively cancel the external excitation.
A known problem with such mount apparatuses is that the commonly piston-shaped moving members have an unfavorable surface area ratio compared to the surface area of the flexible body, thus requiring a relatively large stroke of the actuator relative to the displacement of the flexible body in order to effectively cancel the external excitation.